Heavy duty electric adapters for two and three wire systems



May 14, 1957 B. DOWICK 2,792,557

HEAVY DUTY ELECTRIC ADAPTERS FOR TWO AND. THREE WIRE SYSTEMS Filed Nov. 10. 1954 INVENTOR. BENJAMIN DOWICK United States Patent-O HEAVY DUTY ELECTRIC ADAPTERS FOR TWO AND THREE WIRE SYSTEMS Benjamin Dowick, Jersey City, N. J. Application November 10, 1954, Serial No. 468,001 1 Claim. (Cl. 339-14) This invention relates to electrical connectors, and more particularly to connectors of the plug or receptacleplug type capable of heavy duty.

One object of my invention is the provision of a connector or adapter which greatly simplifies connections of three wire plugs, enabling the latter to be connected to presently installed two wire systems, thereby saving, in the aggregate, large amounts of material, labor, time, and money which would otherwise have to be expended to install a three wire system where three-wire plugs have to be used, as with air conditioners and other electrical appliances, such as clothes washers, for example, and as now required by underwriters for all appliances.

Another object of my present invention is to provide an electric connector such as a plug or receptacle-plug which, while using standard outlets and standard plug prongs to fit such outlets, are adapted to carry relatively heavy electric loads without becoming overheated and causing destruction oftheconnector as now often happens dueto overloading by one or several connections, thereby eliminating presently existing fire hazards, it being known that the standard plugs and not the feed lines are the weak points or current-limiting components. My new connector is particularly valuable for use with appliances that draw relatively heavy currents, as air conditioners, heating devices, washers, etc., and especially avoids the dangers now existing when several such appliances are connected to a single outlet by a standard plug or adapter.

My present invention provides an adapter capable of receiving a three-pronged plug, and in a simple manner provides for the grounding of the third prong of such plug in connection with or relative to the standard wall receptacle, the latter being preferably of the usual double outlet type.

The new adapter provides greater safety when a heavy current is drawn from the power lines and thru the adapter or connector, and to that end has a plurality of sets of standard-sized prongs which are electrically connected in parallel, whereby the current-carrying capacity of the adapter is multiplied, it being understood that I it has not heretofore been possible to double the currentcarrying capacity of the prongs without correspondingly enlarging the contact members in the presently-installed outlets and the size of the feed wire connected thereto, which of course would be expensive to do.

Another advantage of the invention resides in the fact that my new adapter, having the advantages aforesaid, and more particularly the safety features, is attached to a wall outlet, or preferably to an adjacent pair thereof, in such manner that, while readily attached to, and removed from, the outlet, appears, and may be regarded for practical purposes as, a permanent fixture, thus discouraging the substitution of an unsafe and ungrounded adapter.

A still further valuable feature of my invention is that a twin connector which may be made in accordance therewith, is adapted to be operative with either a 2 P n d ay 4 ..1 51

pronged or 3-pronged plug or with both simultaneously, and in both instances has the advantages stated above.

Other advantages will be apparent to those skilled in the art on reading the following matter in connection with the accompanying drawings.

In the drawings, which illustrate one form of my in vention,

Figure 1 is an exploded view showing a wall outlet fixture, a finishing plate, the novel adapter and associated parts, and the relative positions of these components before assembly;

Fig. 2 is a bottom plan view of the novel adapter; and

Fig. 3 is a view showing the use of a screw, etc., to secure the adapter to the outlet receptacle, also for groundl ing the finishing plate, and for holding the latter in place, and further, for grounding the third or groundv prong of a three-pronged plug inserted in the adapter.

Referring to the drawings for a more detailed description thereof, the numeral 7 indicates a standard twin wall or floor outlet fixture in perspective, and as having the usual two pairs of openings, 8 and 9 respectively, for the usual reception of plug connectors. The view also shows the feed line 10 and the usual threaded aperture 12 for the reception of a screw which passes thru a central aperture 14 in a finishing plate 15 and serves to hold the plate to a wall. The outlet receptacle 7 is also shown with the standard bar 17 having its ends (one shown) projecting from the insulating casing of the outlet, the projecting ends of said bar, as known, being adapted to be secured to a grounded metallic receptacle box and thereby ground the plate, it being understood I that the mentioned screw passing thru the finishing plate makes contact at its inner end with the bar 17.

The adapter 20 of this invention comprises an insulat-' ing casing 21 which has a central threaded aperture 22 passing therethru transversely to receive a screw 23 which also passes thru the aperture 14 of the plate 15 and into the aperture 12 of the outlet 7 to contact the bar 17 of the latter and thus ground the plate and hold the latter in place, as aforesaid, and further to secure the adapter to the wall outlet as a permanent fixture, for the purpose explained in the introductory explanation. The adapter, as shown in Figure 1, has two sets of openings, 25 and 26 respectively, for the reception of pronged plugs. The set of openings 25 is shown as comprising three slots, while set 26 has two, the former set being for the reception of a three-pronged plug having one grounding prong, While the latter set have two slots to receive the usual two-pronged plug. Set 25 is used for such appliances as air conditioners, clothes washers, etc., which require grounding. It is to be understood that the set of openings 26 may also have three openings and, when desired set 25 may have only two openings or slots.

It will be seen from Figure 2, which shows a bottom plan view of the adapter 20, that it comprises two sets or pairs of prongs 28 and 29 respectively; these are connected to the usual contactors within the set of openings 26 and within 2 of the 3 openings of set 25. Set 28 fits into the pair of openings 8 and set 29 fits into the pair of openings 9, of the outlet receptacle 7, it being understood that sets 8 and 9 have therein the usual spring contactors to receive and electrically contact plug prongs. It will also be seen from Figure 2 that corresponding prongs of sets 28 and 29 are electrically connected by metallic bars 3%) and 31 respectively, being therefore in parallel, so that a plug inserted in either openings 25 or 26, or plugs inserted in both, will draw current thru all 4 prongs of the adapter. It is possible of course to overload the adapter 20 with its 4 prongs, as any electrical device may be overloaded, but the capacity is much increased over a two-pronged adapter or plug, even when plugs are connected into 'both sets of openings 25 and 26, provided both plugs are not connected to appliances which draw very heavy currents. It is also to be: noted that; one: ofi'the twcr sets ofgopenings'for plug reception, in the adapter, may be. omitted, so: that only one plugmay' be used. and this one draw current; thru the: 4 prongs,or, even with the12i sets: of; openings, only one set need be plugged into at a. time if: the: current drawn is very heavy.

It will now be shown how provision is made: for grounding an appliance: when this'i'si'necessary, and how the; plate is also grounded by: part of the same means. As seeniin. Fig. the center of the inner side or back of'the adapter 20 around the. end: of opening 22' which received the: screw 23.. This. ring is. part of a conducting member which includes end parts 35 and 36. Part 35 is integral with the. usual type of connected. pair of spring conta-ctors provided to. grip a prong, andin this case. such contactors are within. the. opening 25a of the. set of openings 25 shown in Fig. 1, said opening 25a being. for the reception of the: ground prong of a plug. The; other similar end 36 shown as connected with ring 33 is used only when the adapter has 2 sets: of 3 openings each. A hollow-sleeve or rivet 37 is inserted in the central aperture 22 of. the adapter and. hasits. front end flared for the purpose. of securing it, and to conform to and contact the head of screw 23. The inner end of the rivet passes thru the ring 33 and is flared out or peened over onto the back of the ring to make good electrical contact. On. that part of the screw 23 between the back of the adapter 20 and the finishing plate 15, a helical coil of spring wire 38 is wound, this coil contacting the inner peened over inner or back end of. said sleeve or rivet, at. its outer end and at its inner end contacts a metallic jamb washer 39 which is placed on: the screw 23, said washer being larger than the opening 14 in plate 15 2,. a. metallic. ring or washer 33 lies. on.

and contacts the outer face of the latter, and thus makes electrical contact with the plate. When the screw 23 is tightened, the coil 38 presses against the end of said rivet at one end and against the jamb washer 39 at the other end, whereby good electrical contact is made between the ring and the plate, thus securely grounding an appliance and the plate, since screw 23, which threadedly engages the bar 17 which is in contact with the usual grounded receptacle box, is thereby grounded. The sleeve or rivet 39 also functions to hold the plate 15 firmly in position.

What is claimed is:

The combination with a duplex electrical outlet comprising a grounding element and adapted to receive prongs in pairs only, of a receptacle-plug adapter comprising pairs of prongs connected into said outlet, said adapter comprising also a plurality of sets of electrical contactors, and having'openings leading to said contactors, two contactors only of each set of contactors being connected to said prongs, at least one set of said sets of contactors of the adapter consisting of three contactors of which one contactor is a ground contactor, a metallic fastener securing said adapter to said duplex outlet, said fastener contacting said grounding element of said outlet, and anelectrical conductor connecting said ground contactor, with said fastener.

References Cited in the file of this patent UNITED STATES PATENTS- 

